Edge connector for field changeable graphics system

ABSTRACT

One embodiment of an edge connector for a field changeable graphics system includes a right angle edge connector having a plurality of contact pins adapted to engage contacts on a graphics card. The edge connector is adapted to interface the graphics card with the motherboard of a computing device, without directly mounting the graphics card to the motherboard. One advantage of the disclosed edge connector is that it is compatible with a plurality of graphics cards and systems, thereby enabling a computing device user to upgrade the existing device&#39;s graphics system. Thus, the user is not forced to purchase an entirely new computing device in order to take advantage of graphics innovations. A further advantage of the disclosed edge connector is that it enables upgrades to low voltage differential signaling (LVDS) features, without the need for additional costly devices capable of operating at LVDS data rates.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to computer hardware and relates more particularly to a field changeable graphics system for a computing device.

2. Description of the Background Art

Contemporary computing devices typically incorporate a graphics card that enables a computing device to rapidly process graphics related data for graphics intensive applications, such as gaming applications. A graphics card generally comprises a printed circuit board (PCB) upon which a plurality of circuit components (such as memory chips and the like) and a graphics processing unit (GPU) are mounted. In “closed platform” computing devices such as laptop computers, cellular telephones and personal digital assistants (PDAs) (i.e., devices that use processors and are not easily changed by a user), the graphics card is mounted directly and permanently to the motherboard of the computing device.

One drawback to mounting the graphics card directly to the motherboard is that this fixed configuration impedes a user's ability to upgrade the computing device's graphics system. Specifically, in order to take advantage of an improved graphics system, the user typically must purchase an entirely new computing device, which is much more costly than a simple replacement of the graphics system in the existing computing device.

A second drawback is that the pace of graphics innovations that can be conveniently delivered to computing device users is hindered, because the implementation of on-board devices is typically limited by a design cycle of approximately nine to twelve months.

Thus, there is a need in the art for a field changeable graphics system for a computing device.

SUMMARY OF THE INVENTION

One embodiment of an edge connector for a field changeable graphics system includes a right angle edge connector having a plurality of contact pins adapted to engage contacts on a graphics card. The edge connector is adapted to interface the graphics card with the motherboard of a computing device, without directly mounting the graphics card to the motherboard.

One advantage of the disclosed edge connector is that it is compatible with a plurality of graphics cards and systems, thereby enabling a computing device user to upgrade the existing device's graphics system. Thus, the user is not forced to purchase an entirely new computing device in order to take advantage of graphics innovations. This advantage is particularly significant for users of portable computing devices, such as laptop computers, cellular telephones and PDAs, or other devices traditionally having fixed graphics functionality such as video game consoles.

A further advantage of the disclosed edge connector is that it enables upgrades to low voltage differential signaling (LVDS) features, without the need for an additional (and typically costly) device that is capable of operating at LVDS data rates.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view illustrating a field changeable graphics system, according to one embodiment of the present invention.

FIG. 2 is a top plan view illustrating a graphics card for use in field changeable graphics system of FIG. 1, according to one embodiment of the present invention;

FIGS. 3A-B are tables illustrating one embodiment of a pinout for the edge connector illustrated in FIG. 2;

FIGS. 4A-C are tables containing contact pin descriptions for each signal type identified in FIGS. 3A-B;

FIG. 5 is a table summarizing the power that must be supplied through an edge connector from a motherboard to a graphics card, according to one embodiment of the present invention;

FIG. 6A is a schematic diagram illustrating a configurable graphics system according to one embodiment of the present invention;

FIG. 6B is a schematic diagram illustrating graphics system according to another embodiment of the present invention;

FIG. 7A is a schematic diagram illustrating a user-upgradeable graphics system, according to one embodiment of the present invention; and

FIG. 7B is a schematic diagram illustrating a user-upgradeable graphics system, according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a side view illustrating a field changeable graphics system 100, according to one embodiment of the present invention. Graphics system 100 is adaptable for use with any type of computing device, including, without limitation, a desktop computer, server, laptop computer, palm-sized computer, personal digital assistant, tablet computer, game console, cellular telephone, computer-based simulator and the like. As will be explained in further detail below in conjunction with FIGS. 6A-7B, graphics system 100 is configured to ensure compatibility with a plurality of field changeable graphics cards.

Generally, graphics system 100 is configured to interface with a computing device motherboard 102 in lieu of a conventional graphics card and includes, without limitation, a graphics card 104 and an interface assembly 150. Graphics card 104 includes a GPU and a plurality of circuit components including memory (not shown) mounted to a first face 101, typically facing away from motherboard 102. Graphics card 104 further comprises a card connector 106 positioned along an edge 105 of graphics card 104 and adapted to engage interface assembly 150. Several embodiments of field changeable graphics cards suitable for use in graphics system 100 are described in co-pending, commonly assigned U.S. patent application Ser. No. ______, filed ______ by Bisson et al. (Attorney Docket No. NVDA/P001196), which is herein incorporated by reference.

As also described in further detail below in conjunction with FIGS. 2-5, graphics system 100 is configured to interface with motherboard 102 without being directly mounted to motherboard 102. This is enabled by interface assembly 150, which includes, without limitation, one or more supports 108 and an edge connector 114. Supports 108 are mounted to motherboard 102 and extend upward therefrom to engage graphics card 104. Supports 108 are adapted to stably maintain graphics card 104 in a spaced-apart orientation relative to motherboard 102. In one embodiment, supports 108 are sized to maintain a distance d between graphics card 104 and motherboard 102 that is approximately 4mm.

Also as described in conjunction with FIG. 2, edge connector 114 is mounted to motherboard 102 and includes a lengthwise channel 116 having a plurality of contacts disposed on upper and lower surfaces 118, 120. The contacts are adapted for engaging card connector 106 on graphics card 104, for routing external and internal interfaces from graphics card 104 to motherboard 102.

FIG. 2 is an isometric view illustrating one embodiment of an edge connector 200 according to the present invention. Edge connector 200 is adapted to route all internal and external interfaces from a graphics card (e.g., graphics card 104 of FIG. 1) to a motherboard of a computing device. Edge connector 200 comprises an elongated body 202 having a longitudinal slot 204 formed therein. Longitudinal slot 204 is sized to receive an edge of a graphics card connector (e.g., card connector 106). In one embodiment, longitudinal slot 204 is sized to accommodate card thicknesses of up to 1.2 mm. Contact pins (not shown) disposed on top and bottom surfaces 206, 208 of longitudinal slot 204 are adapted to interface with contacts on a card connector.

FIGS. 3A-B are tables illustrating one embodiment of a pinout for edge connector 200. Each contact pin on edge connector 200 is associated with an individual signal (e.g., power input, ground and the like). In the embodiment illustrated, edge connector 200 utilizes a 230-pin card-edge connection system, wherein contact pins on edge connector 200 are rated for 0.5 A steady state current. FIGS. 4A-C are tables containing contact pin descriptions for each signal type identified in FIGS. 3A-B. Input/output classifications in FIGS. 4A-C are relative to a GPU mounted on the graphics card. References to “MXM module” indicate a graphics card according to the present invention.

FIG. 5 is a table summarizing the power that must be supplied by the motherboard to a graphics card, i.e., through edge connector 200, according to one embodiment of the present invention. If the motherboard's power supply equals or exceeds the power requirements summarized in FIG. 5, a graphics card interfaced to an edge connector according to the present invention (e.g., edge connector 200) will run at full speed. However, the interface will also allow a graphics card to detect power supply limitations of the motherboard and to automatically throttle its clocks to stay within the limits of the available power.

In addition to the power requirements summarized in FIG. 5, a motherboard must meet a plurality of additional system requirements in order to effectively interface to a graphics system of the present invention. For example, in one embodiment, the motherboard is required to place a serial ROM that connects to the DDCC_DAT and DDCC_CLK signals (e.g., connector pins 220 and 222 in FIG. 3B). In addition, the motherboard must provide back drive isolation and level shifting, for all DDC lines, VGA_HSYNC and VGA_VSYNC signals (e.g., connector pins 151 and 153). Furthermore, the motherboard must provide power to the computing device LVDS panel, and must route all RGB signals and TV_out signals with 37.5 Ohms impedance. In one embodiment, the motherboard is also required to have output filters on all VGA output lines and on all TV output lines, the filters being positioned as closely as possible to the connector pins. Input filters are required on the DVI_B_HPD and DVI_A_HPD lines (e.g., connector pins 191 and 217), and the graphics card will provide level shifting and clamping for the DVI_B_HPD and DVI_A_HPD signals.

In one embodiment, an edge connector according to the present invention (e.g., edge connector 200) is adapted to detect a graphics mode of a computing device, and to cause display interfaces to be routed from a graphics card to the motherboard accordingly. Specifically, the PRSNT#1 connector pin on the edge connector (e.g., pin 134 in the pinout of FIGS. 3A-B) is adapted to detect if a graphics upgrade, such as any one of the graphics cards disclosed in U.S. patent application Ser. No. ______, has been implemented in the computing device. In one embodiment, a voltage detected by the PRSNT #1 connector pin indicates the presence of a graphics upgrade. For example, a high voltage detected by the PRSNT#1 connector pin indicates that a “dummy” or “loop-through” card (e.g., a card with no graphics processing unit) is interfaced to the edge connector, as explained in further detail in conjunction with FIGS. 6A and 7A below. Alternatively, a low voltage detected by the PRSNT#1 connector pin indicates that a graphics upgrade such as a graphics card is interfaced to the edge connector, as explained in further detail in conjunction with FIGS. 6B and 7B below. [Note to inventors: What is considered a “high” or “low” voltage for the purposes of determining which card is in?]

FIG. 6A is a schematic diagram illustrating a configurable graphics system 600, according to one embodiment of the present invention. The output topology illustrated in FIG. 6A depicts a manufacturing-end graphics configuration (i.e., graphics system 600 is incorporated during assembly of the computing device). Graphics system 600 comprises a standard integrated graphics processor (IGP) 612 (driven in one embodiment by a Northbridge chip set, not shown), a loop-through card 650, and a plurality of display panels 604-610 for video graphics array (VGA), television (TV), low voltage differential signaling (LVDS) and digital video interface (DVI) signals. The display output signals are generated by IGP 612 in conjunction with loop-through card 650, as described further below.

Loop-through card 650 may be implemented in graphics system 600 in place of a conventional LVDS capable device. As described above, the PRSNT #1 connector pin on the edge connector detects a high voltage and sends a corresponding signal to the Northbridge chip set indicating the presence of loop-through card 650. Consequently, the Northbridge outputs LVDS signals to the edge connector, in one embodiment connecting the signals to the IGP_LVDS connector pins [Note to inventors: Which pins are these? Do not see on pinout]. The passive loop-through card 650 completes the circuit paths between the output signals and the LVDS panel input signals. Thus, the edge connector, in conjunction with loop-through card 650, enables a computing device user to implement LVDS features without the need to implement complex (and costly) traditional LVDS-capable devices.

In one embodiment, the graphics system 600 further supports DVI. In this embodiment, DVI signals are output to the DVI_A connector pins (e.g., connector pins 219, 221, 225, 227, 231, 233, 237 and 239 in FIG. 3B) on the edge connector and routed to loop-through card 650, which further comprises a transmission minimized differential signaling (TMDS) transmitter for driving TMDS outputs on received signals. TV and VGA signals are output from the Northbridge chip set to IGP 612 in accordance with standard IGP operation.

In one embodiment, graphics system 600 further comprises a plurality of stuffing resistors 614 a and 614 b (shown in phantom) adapted for completing the circuits from IGP 612 and from loop-through card 650 to display panels 604-610. During assembly of a computing system, a manufacturer may configure graphics system 600 to operate in the mode described (e.g., incorporating loop-through card 650) by closing the circuit paths through resistors 614 a and leaving the circuit paths through resistors 614 b open.

Alternatively, as illustrated in FIG. 6B, a manufacturer may close the circuit paths through resistors 614 b and leave the circuit paths through resistors 614 a open, in order to implement an active graphics card. In this embodiment, graphics system 600 comprises a graphics card 660 in place of loop-through card 650. Graphics card 660 may be configured in a manner similar to any one of the graphics cards described in U.S. Pat. No. ______. Graphics card 660 generates substantially all display output signals, as described further below.

As described above, the PRSNT #1 connector pin on the edge connector detects a low voltage and sends a corresponding signal to the Northbridge chip set indicating the presence of graphics card 660. Consequently, the Northbridge outputs a peripheral component interface (PCI) Express signal to the edge connector, which routes the signal to graphics card 660. VGA, TV, LVDS and DVI signals are subsequently generated by graphics card 660. As described above, stuffing resistors 614 b complete the circuits from graphics card 660 to display panels 604-610.

FIG. 7A is a schematic diagram illustrating a graphics system 700 according to one embodiment of the present invention. The output topology illustrated in FIG. 7A depicts a user-upgradeable configuration. That is, a user may upgrade graphics system 700 on demand, by simply exchanging one field-exchangeable graphics card for another. Graphics system 700 is substantially similar to graphics system 600 illustrated in FIG. 6A and comprises an IGP 712, a loop-through card 702, and a plurality of display panels 704-710 for VGA, TV, LVDS and DVI signals. The display output signals are generated by IGP 712 in conjunction with loop-through card 702, as described further below.

LVDS and DVI signals are output by the Northbridge to the edge connector as described above in conjunction with FIG. 6A. The passive loop-through card 702 completes the circuit paths between the output signals and the LVDS and DVI panel input signals. TV and VGA signals are output from the Northbridge chip set to IGP 712 in accordance with standard IGP operation. In one embodiment, graphics system 700 further comprises a plurality of muxes 714 adapted for receiving and transmitting IGP-initiated signals (e.g., for VGA and TV signals). During assembly of a computing system, a manufacturer may configure graphics system 700 to operate in the mode illustrated in FIG. 7A (e.g., incorporating loop-through card 702) as a default.

FIG. 7B is a schematic diagram illustrating graphics system 700 in an upgraded mode. Graphics system 700 is substantially similar to graphics system 600 illustrated in FIG. 6B and comprises an IGP 702, a plurality of display panels 704-710 for VGA, TV, LVDS and DVI signals and an active graphics card 760 in place of loop-through card 702.

When the presence of graphics card 760 is detected, the Northbridge sends a PCI Express signal through the edge connector and to graphics card 760. Muxes 714 are configured to automatically reconfigure to connect VGA and TV circuit paths to graphics card 760.

An edge connector according to the present invention may thus be configured to enable a computing device user to upgrade an existing device's graphics system with minimal expense. Because the edge connector is adapted to work with a plurality of field-changeable graphics cards, the user is not forced to purchase an entirely new computing device in order to take advantage of graphics innovations. This advantage is particularly significant for users of portable computing devices, such as laptop computers and PDAs, in which graphics systems are frequently difficult or impossible to alter.

A further advantage of the disclosed edge connector is that it enables upgrades to LVDS features. Typical devices capable of operating at LVDS data rates tend to be rather costly. However, by configuring the edge connector of the present invention to enable LVDS signals to “loop through” a passive card, the versatility of the graphics system is enhanced with minimal cost to the user.

Moreover, though the present invention has been described in terms of graphics cards, those skilled in the art will appreciate that the invention may be adapted for use with other devices that are typically hardwired to a motherboard, such as audio chips and the like.

Thus, the present invention represents a significant advancement in the field of computing device graphics systems. An edge connector is provided that enables a plurality of field-changeable graphics systems to interface to a single computing device motherboard. The edge connector thus maximizes the graphics options that may be implemented in an existing computing device, allowing computing device users greater ability to take advantage of graphics innovations.

Furthermore, the present invention grants more flexibility to computing device manufacturers, since it removes the approximately nine to twelve month design cycle for on-board implementations. The present invention also enables the build-to-order, stock-to-order and field repair of any of the systems disclosed, which is a significant advancement for a global economy having needs for just-in-time manufacturing and inventory management.

Those skilled in the art will appreciate that although the present invention has been described in the context of closed platform computing devices such as laptop computers, cellular telephones and PDAs, the present invention may be adapted for use with any device that uses a processor and is not easily changed by a user, such as automotive navigation systems, entertainment systems, all-in-one personal computers, printers and the like. Moreover, although the present invention has been described in the context of standardized, field changeable graphics cards, the present invention may be deployed in other form factors such as credit card polymer substrates with embedded chips, and postage stamp-sized, self-contained devices, among others.

Although the invention has been described above with reference to specific embodiments, persons skilled in the art will understand that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The foregoing description and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. 

1. Connector for interfacing a graphics system to a computing device motherboard comprising: a plurality of connector pins adapted for routing signals from a motherboard to a field-changeable graphics card, wherein a first connector pin of the plurality of connector pins is adapted to detect the presence of the field-changeable graphics card and to cause the signals to be routed accordingly.
 2. The connector of claim 1, wherein the connector is a right-angle edge connector mounted to the motherboard.
 3. The connector of claim 1, wherein the connector comprises 230 connector pins.
 4. The connector of claim 1, wherein a voltage detected by the first connector pin indicates a mode of the interfaced graphics system.
 5. The connector of claim 4, wherein a high voltage detected by the first connector pin indicates that a passive loop-through card is interfaced to the connector.
 6. The connector of claim 5, wherein the connector is adapted to cause a low voltage differential signaling (LVDS) signal to be routed from a driver through the loop-through card to an LVDS display panel.
 7. The connector of claim 5, wherein the connector is adapted to cause a digital video interface (DVI) signal to be routed from a driver through the loop-through card to a DVI display panel.
 8. The connector of claim 7, wherein the loop-through card comprises a transmission minimized differential signaling (TMDS) transmitter for driving TMDS outputs on DVI signals.
 9. The connector of claim 4, wherein a low voltage detected by the first connector pin indicates that an active graphics card is interfaced to the connector.
 10. The connector of claim 10, wherein the connector is adapted to cause a peripheral component interface (PCI) express signal to be routed from a driver to the active graphics card.
 11. The connector of claim 10, wherein the active graphics card is adapted to receive the PCI express signal from the driver in order to generate a plurality of output display signals.
 12. The connector of claim 11, wherein the active graphics card is adapted to generate low voltage differential signaling (LVDS), digital video interface (DVI), television (TV) and video graphics array (VGA) signals.
 13. The connector of claim 1, wherein the connector is configured to allow a user of a computing device to replace a graphics system post-assembly.
 14. The connector of claim 1, wherein the connector is adapted to allow a manufacturer to configure a single motherboard for at least two different graphics modes.
 15. The connector of claim 1, wherein the connector is further adapted to maintain a graphics card in a substantially parallel, spaced apart relation relative to the motherboard.
 16. Apparatus comprising: a motherboard usable in a laptop computing device; a central processing unit mounted to the motherboard; an integrated graphics processor (IGP) mounted to the motherboard; a field-changeable graphics card interfaced to the motherboard; and a plurality of stuffing resistors adapted for interfacing the field-changeable graphics card to a plurality of output display panels, wherein the field-changeable graphics card resides in an independent, spaced-apart relation relative to the motherboard.
 17. The apparatus of claim 16, wherein the apparatus further comprises an edge connector mounted to the motherboard and comprising a plurality of connector pins adapted for engaging the field-changeable graphics card in order to route signals from the motherboard to the field-changeable graphics card.
 18. The apparatus of claim 17, wherein the field-changeable graphics card is a passive loop-through card.
 19. The apparatus of claim 18, wherein a first set of stuffing resistors is adapted to interface the passive loop-though card to an output display panel for low voltage differential signaling (LVDS) signals.
 20. The apparatus of claim 19, wherein a first connector pin on the edge connector is adapted to cause the LVDS signals to be routed from a driver, through the passive loop-through card and to an LVDS output display panel.
 21. The apparatus of claim 19, wherein the first set of stuffing resistors is further adapted to interface the passive loop-through card to an output display panel for digital video interface (DVI) signals.
 22. The apparatus of claim 21, wherein the passive loop-through card further comprises a transmission minimized differential signaling (TMDS) transmitter for driving TMDS outputs on DVI signal.
 23. The apparatus of claim 19, wherein the first set of stuffing resistors is further adapted to interface the IGP to video graphics array (VGA) and television (TV) output display panels.
 24. The apparatus of claim 17, wherein the field-changeable graphics card is an active graphics card comprising a graphics processing unit (GPU).
 25. The apparatus of claim 24, wherein the edge connector is adapted to cause a peripheral component interface (PCI) express signal to be routed from a driver to the active graphics card.
 26. The apparatus of claim 25, wherein the active graphics card is adapted to generate VGA, TV, LVDS and DVI signals.
 27. The apparatus of claim 26, wherein a second set of stuffing resistors is adapted to interface the active graphics card to output display panels for VGA, TV, DVI and LVDS.
 28. Apparatus comprising: a motherboard usable in a laptop computing device; a central processing unit mounted to the motherboard; an integrated graphics processor (IGP) mounted to the motherboard; a field-changeable graphics card Interfaced to the motherboard; and a plurality of muxes adapted for interfacing the field-changeable graphics card to a plurality of output display panels, wherein the field-changeable graphics card resides in an independent, spaced-apart relation relative to the motherboard.
 29. The apparatus of claim 28, wherein the apparatus further comprises an edge connector mounted to the motherboard and comprising a plurality of connector pins adapted for engaging the field-changeable graphics card in order to route signals from the motherboard to the field-changeable graphics card.
 30. The apparatus of claim 28, wherein the field-changeable graphics card is a passive loop-through card.
 31. The apparatus of claim 30, wherein the plurality of muxes is adapted to interface the passive loop-though card to an output display panel for low voltage differential signaling (LVDS) signals.
 32. The apparatus of claim 31, wherein a first connector pin on the edge connector is adapted to cause the LVDS signals to be routed from a driver, through the passive loop-through card and to an LVDS output display panel.
 33. The apparatus of claim 31, wherein the plurality of muxes is further adapted to interface the passive loop-through card to an output display panel for digital video interface (DVI) signals.
 34. The apparatus of claim 33, wherein the passive loop-through card further comprises a transmission minimized differential signaling (TMDS) transmitter for driving TMDS outputs on DVI signal.
 35. The apparatus of claim 31, wherein the plurality of muxes is further adapted to interface the IGP to video graphics array (VGA) and television (TV) output display panels.
 36. The apparatus of claim 29, wherein the field-changeable graphics card is an active graphics card comprising a graphics processing unit (GPU).
 37. The apparatus of claim 36, wherein the plurality of muxes is adapted to automatically reconfigure to receive and transmit signals from the active graphics card.
 38. The apparatus of claim 36, wherein the edge connector is adapted to cause a peripheral component interface (PCI) express signal to be routed from a driver to the active graphics card.
 39. The apparatus of claim 38, wherein the active graphics card is adapted to generate VGA, TV, LVDS and DVI signals.
 40. Connector for interfacing a field-changeable card to a computing device motherboard comprising: a plurality of connector pins adapted for routing signals from a motherboard to a field-changeable card, the field-changeable card having circuitry for performing a rendering function for use in the computing device, wherein a first connector pin of the plurality of connector pins is adapted to detect the presence of the field-changeable card and to cause the signals to be routed accordingly.
 41. The connector of claim 40, wherein the field-changeable card is a graphics card comprising a graphics processing unit.
 42. The connector of claim 40, wherein the field-changeable card is an audio chip.
 43. The connector of claim 16, wherein the connector is further adapted to maintain a graphics card in a substantially parallel, spaced apart relation relative to the motherboard.
 44. The apparatus of claim 17, wherein a first connector pin of the plurality of connector pins is adapted to detect the presence of the field-changeable graphics card and to cause the signals to be routed accordingly.
 45. The apparatus of claim 17, wherein the connector is a right-angle edge connector mounted to the motherboard.
 46. The apparatus of claim 17, wherein a voltage detected by the first connector pin indicates a mode of the interfaced graphics system.
 47. The connector of claim 46, wherein a low voltage detected by the first connector pin indicates that an active graphics card is interfaced to the connector.
 48. The apparatus of claim 18, wherein a high voltage detected by the first connector pin indicates that a passive loop-through card is interfaced to the connector.
 49. The connector of claim 29, wherein the connector is further adapted to maintain a graphics card in a substantially parallel, spaced apart relation relative to the motherboard.
 50. The apparatus of claim 29, wherein a first connector pin of the plurality of connector pins is adapted to detect the presence of the field-changeable graphics card and to cause the signals to be routed accordingly.
 51. The apparatus of claim 29, wherein the connector is a right-angle edge connector mounted to the motherboard.
 52. The apparatus of claim 29, wherein a voltage detected by the first connector pin indicates a mode of the interfaced graphics system.
 53. The connector of claim 52, wherein a low voltage detected by the first connector pin indicates that an active graphics card is interfaced to the connector.
 54. The connector of claim 29, wherein a high voltage detected by the first connector pin indicates that a passive loop-through card is interfaced to the connector. 